The Equine Skeleton How Does Bone Grow and How Do Abnormalities in the Developmental Process Affect Soundness?

Long bones develop from cartilage by a process of endochondral (within cartilage) ossification (Fig 1). In the fetus, the bone anlages (early bone templates) are composed entirely of cartilage. Centers of ossification (bone formation) develop in the center of the future long bone (diaphysis) and also at the ends of these long bones (epiphysis). As ossification proceeds, a bony epiphysis develops at each end and a bony diaphysis develops in the center. Between these two centers of ossification is a metaphyseal growth plate (also called physis) and this is what enables the limb to continue to lengthen after birth as the foal grows. Eventually, the epiphyseal center of ossification and the diaphyseal center of ossification will unite and this results in bony closure of the physis.